I think of it as giving some representation to the land itself (and it's natural resources) as represented by the people who work and live there.
Harvard wants to send another 40. Science is, after all, more important these days than natural resources. Just compare Switzerland (absolutely nothing of value in the ground) to Equatorial Guinea (top-10 oil reserves).
The one export market where the US dominates is culture. Mind if Hollywood sends in a few representatives?
But I do think that farmers (for example) contribute a lot to a country and would lack voting power in a purely population based presidential election system.
I'd note that this argument goes against my politics: Farmers as a block are rarely progressives.
Edit: Elsewhere gameman144 explains my point better than I have been able to:
> The top four states have roughly a third of the national population; if federal policy were enacted purely by population, why shouldn't they allocate all federal funds to themselves and deprive other states entirely? The Senate and the electoral college give enough of an advantage to small states that, even though no one or two small states are liable to flip an election by themselves, they are still able to have a voice in federal policy by coalition-building.